Impacter bounce shock eliminator



Dec. 10, 1963 J. K. MUREK Y 3,113,476

IMPACTER BOUNCE SHOCK ELIMINATOR Filed Aug. 24, 1961 s Sheets-Sheet a JfiIf/"KMVZIA INVENTOR.

Dec. 10, 1963 J. K. MUREK 3,113,476

IMPACTER BOUNCE SHOCK ELIMINATOR Filed Aug. 24. 1961 5 Sheets-Sheet 4 6 I JOJf/ A. 44%;? i INVENTOR.

BY j

Dec. 10, 1963 J. K. MUREK 3,113,476

IMPACTER BOUNCE SHOCK ELIMINATOR Filed Aug. 24. 1961 5 Sheets-Sheet 5 7? i 54 INVENTOR.

BY Syd";

United States Patent 3,113,476 IMPACTER BOUNCE SHOCK ELIMINATOR Josef K. Murek, San Diego, Calif., assiguor to General Dynamics Corporation, San Diego, Calif., a corporation of Delaware Filed Aug. 24, 1961, Ser. No. 133,673 5 Claims. (Cl. 7842) This invention relates to an impacter bounce shock eliminator for impact forming machines, and more particularly to an assembly that eliminates rebound shock when used with or in combination with impact forming machines, which machines form a workpiece to a desired configuration preferably through an initial or single impact of an impacting column. The bounce shock eliminator functions to eliminate the detrimental and destructive shock resulting from bouncing impacts that occur between a workpiece and the forming die and functions to contain or absorb the shock that results from bouncing or rebounding. While the present invention is adapted for advantageous use in combination with any impact forming machine, it is particularly advantageous when used in combination with high velocity impacting machines that have relatively low mass impacting columns.

In forming workpieces with impact type forming machines in general, or with high velocity, low mass, impact forming machines, it is often desirable, if not necessary, to form the workpiece or billet by a single, initial impact of the impacting column. However, in many forming operations, the entire momentum of the impacting column is not absorbed in performing work on the workpiece in the initial impact of the impacting column. Thus unabsorbed momentum still exists in the impacting column after a single impact. This unabsorbed momentum causes the impacting column to bounce back from the workpiece after initial impact and to again impact the workpiece causing further forming or deformation of the workpiece to occur. Multiple impact shock from rebounding can destroy the desired workpiece configuration that was accomplished by the initial impact, and it is diflicult, if not possible, to con sistently produce finished workpieces to any desirable degree of close tolerances where there is impacting shock from bouncing or rebounding of the impact column. In addition it is extremely difficult to predict or accurately control the degree of forming that will result from multiple impacting. Therefore, it is desirable that multiple impacting be eliminated. The workpiece can then be formed to the desired configuration and dimensions through a single impact, regardless of whether the full momentum of the impacting column has been absorbed through the single impact.

Bouncing of the impacting column is particularly troublesome where high velocity impacting machines are used, since high velocity machines normally use a relatively low mass impacting column. The high velocity and low mass of the impacting column are somewhat conducive to very rapid bouncing that is difiicult to eliminate. While the impact shock on the workpiece caused by bouncing can in some instances be directly transferred to other portions of the machine, such as to the frame and then to the supporting base, such a means of reducing rebound impact shock often has little effect in protecting the workpiece. Further such a means normally causes the machine to vibrate excessively and with such force that either the momentum of the impacting column has to be reduced or the frame and supporting base had to be made undesirably large and heavy.

Accordingly it is an object of this invention to provide an improved bounce shock eliminator that substantially eliminates the impact shock from bouncing that occurs in impact forming machines.

It is another object of this invention to provide an improved bounce shock eliminator that substantially eliminates the bouncing shock between the die and the workpiece in an impact forming machine and leaves the bouncing shock in the impacting column.

The present invention is directed to a shock eliminator means in combination with an impacting machine for forming materials through impact between an impacting thrust means and a bolster means during a forming impact stroke. The shock eliminator means includes a telescoping mechanism that utilizes a pressurized medium between the telescoping parts. The eliminator means is positioned in the line of force of the impacting thrust means and upon impact the telescoping mechanism telescopes against the trapped pressurized medium. After the forming impact, the mechanism then expands telescopically under the force of the pressurized medium. This expansion holds the workpiece and the forming die, used in the machine, in contact during the interval following the forming impact stroke and provides a cushioning eifect between the impacting thrust means and the work or bolster in the line of shock created by the impact. The impacting means can then bounce or rebound after impact relative to the work or bolster means without causing further forming of the workpiece. In the impact stroke, the force and momentum of the impact forming means is of such a large magnitude that the shock eliminator means is telescoped to a metal to metal contact thus permitting the maximum degree of forming shock to be applied to the work. Thereafter the pressurized medium within the shock eliminator means is of sulficient magnitude to absorb the remaining momentum of the impact forming means that was not spent in the initial forming impact stroke.

The bounce shock eliminator means generally com prises a cylindrical member having a movable piston member mounted therein. A recess is provided between the inner closed end of the cylindrical member and the end of the piston member, which recess allows a pressurized medium such as air or gas to be compressed therein when the end of the piston member is forced against the inner surface of the closed end of the cylindrical member. Under an initial condition, the piston member is forced to an extended telescoped position by air inserted under pressure between the end of the piston member and the cylindrical member. Upon impact of the impact forming means against the work or bolster means, the end of the piston member is forced into contact with the closed end of the cylinder member. This effects a metal to metal contact between the impact forming means and the bolster means with the workpiece and bounce shock eliminator device sandwiched therebetween.

When the end of the piston member is against the closed end of the cylindrical member, the air under pressure in the enclosed space therebetween is forced into the recess. After the forming impact stroke, the air pressure in the recess forces the piston member to move away from the end of the cylindrical member. This movement is sufficient to expand the length of the combined cylindrical and piston members telescopically, holding the die and workpiece together while providing an air cushion for absorbing the rebound shock of the impact forming means. This air cushion absorbs the remaining momentum of the impact forming means that was not expended in the forming impact stroke.

The exact nature of this invention as well as other objects and advantages therefor will be readily apparent from consideration of the following specification relating to the drawings in which:

FIGURE 1 is an elevational view of a wall-mounted, high-velocity, impact forming machine including the impacter bounce shock eliminator;

FIGURE 2 is a partly in section view of the highvelocity, impact forming machine shown in FIGURE 1;

FIGURE 3 is an enlarged view, partly in section, of the shock absorber assembly utilized in the high-velocit impact forming machine;

FIGURE 4 is a sectional side View of the bounce shock eliminator assembly and portions of the impact forming machine when the shock eliminator assembly is in the initial loaded condition;

FIGURE 5 is a sectional side view of the bounce shock eliminator assembly and portions of the impact forming machine at the time of impact;

FIGURE 6 is a sectional side View of the bounce shock eliminator assembly and portions of the impact forming machine after the workpiece has been formed and the elimination of shock from bouncing is being accomplished;

FIGURE 7 is an end view taken along lines VII-VII of FIGURE 4;

FIGURE 8 is a side elevational view of an alternate embodiment of the invention.

Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views. There is shown in FIGURES 1 and 2 an impact forming machine of the high-velocity, low-mass type that embodies, as a combination thereof, the bounce shock eliminator assembly 28. The forming machine includes a frame structure 12 that is slidably mounted in a foundation formed by foot assemblies 142 that in turn are attached to a support wall IS. The frame structure includes three guide rods 39 to which at one end an actuator end wall 126 is secured by nuts and lock rings 82. At the other end of the frame member 12, a bolster 132 is secured to the guide rods 367 by nuts 130. Lock sleeves 128 provide for adjustment of the axial position of the bolster 132 along the length of guide rods 30.

The two guide rods 30 that are adjacent the foundation are slidable in bearings 232 that are supported within foot assemblies 142, as illustrated in FIGURES l and 3. Disposed about each of the two guide rods 3% is a shock absorber assembly 234 that extends between the two foot assemblies 142. Each of the shock absorber assemblies 234 includes two cylindrical sections 236 and 238, that are secured in clamped relation with an orifice ring 240 by end caps 242 and 244. The end caps are provided with seal rings in appropriate grooves to provide pressure sealing between the cylindrical sections 236 and 238 and the guide rod 30. The orifice ring 246 has a plurality of small axially extending orifices, as shown, and is provided with appropriate seal rings for pressure sealing. A11 annular piston 246 is secured to the guide rod 30 between a pair of split lock rings 25%. Annular piston 248 is similarly secured. The annular pistons 245 and 248 are provided with seal rings in appropriate grooves for pressing sealing between the cylindrical housing 236 and 238 and the guide rods 34 From the foregoing and from FIGURE 3, it will be observed that a coaxial pressure chamber 252 is defined between the orifice ring 246 and annular piston 246, and that a similar chamber 254 is defined between the orifice ring 240 and annular piston 248. It will be observed that a coaxial pressure chamber 256 is defined between annular piston 246 and end cap 242, and that a similar chamber 258 is provided between the annular piston 248 and end cap 244. Chambers 252 and 254 are filled with oil through openings 260 and 262, respectively, in which appropriate filter plugs are threaded. Pneumatic valves 264 are provided for the provision and maintenance of air pressure in chambers 256 and 258.

The frame structure 12 and an actuator housing 106 together constitute a reaction assembly. The actuator housing is secured as previously stated on the guide rods 3% by nuts 8i and lock rings 82 in appropriate openings in end wall 126 of the housing and through appropriate openings in the end wall 122. The guide rods 39 merely extend through the openings in the end Wall 122 with a snug sliding fit, however the end wall 122 can be held to the rods 3% by an appropriate nut and lock ring arrangement if desired. As illustrated in FIGURE 2, the actuator end walls 122 and 126 are provided with circularly arranged openings for accommodating tie bolts 90. Cylindrical sections $4 and 112, orifice plate 146, and end fitting plates 81 and 114 are secured in clamped relation with the end walls 122 and 126 by the tie bolts S it. Pressure sealing for the actuator housing 106 is provided by resilient seal rings in appropriate grooves in the fitting plates 81 and 114- and in the orifice plate 146. An orifice 1% is provided in the orifice plate 1% for a purpose that is hereinafter explained. The cylindrical actuator housing may be considered as divided into pressure chambers 96 and 110 by the orifice plate 146. A passage 154 in the orifice plate 146 inter-connects chamber 96 with a source of pressure (not shown). The orifice plate has a passage 98 therein. A passage 11%, extending through fitting plate 114 and end wall 122, is provided with an appropriate coupling that inter-connects chamber 11% with a source of pressure (not shown).

An actuator piston 193 is positioned in chamber 119. A circular seal base 152 is secured by a bolt in an appropriate recess in the face of the piston and is provided with a groove in which a circular resilient pressure seal 14' is secured by bonding. As shown, circular seal 14% is adapted to encircle orifice 15% when the actuator piston M8 is sealed against the orifice plate 146. An annular sealing element 192 in a peripheral groove in the piston M38 provides pressure sealing between the piston and the cylindrical section 3112. Bearing rings Tilt) are disposed on both sides of the sealing element in recesses in th piston periphery to reduce sliding friction and to maintain alignment between the piston and the cylindrical section. A reduced end portion of the impact member or thrust column 118 is secured in the opening in the piston. The thrust column extends through aligned openings in fitting plate 114 and end wall 122, and is slidably received in a bearing disposed opening 129 of the end wall. A seal ring in the groove within this opening provides pressure sealing. A die element at the end of the impact member 118 confronts a cooperating die member 136 on anvil 134, that is secured to bolster 132 in confronting relation with the thrust column 118. A workpiece 138 is positioned to be impacted between the thrust column and the die member, as shown in FIG- URE 2.

From the foregoing description, it will be understood that the impacting machine has a frame '12 and an actuator housing 106 that is secured to the shock absorber assembly 234. The shock absorber assembly 234 is slidably mounted to base member 142 that is attached to the wall 18. The actuator piston 16 8 and thrust column 1-18 are movable relative to the actuator housing and the frame. The actuator piston 198 is used to impart high acceleration to the impacting thrust means or thrust column 118 as follows. A setting pressure is first introduced into chamber 110 through passage 116. This pressure acts upon the thrust column side of piston 1% and urges the piston against orifice plate 1-46. This compresses the circular resilient seal 143 against the surface of the orifice plate 146 to effect a positive pressure seal that isolates chamber 118 from chamber 96. A second and higher pressure is established in chamber 96 through passage 154 in the orifice plate 146. This actuating pressure acts upon the area of the pressure seal 52 and is predetermined to balance the force exerted by the resilient pressure upon the larger area on the opposite side of the piston.

To trigger the actuator, the pressure in chamber 96 is increased by a pressure differential sufficient to unbalance the forces upon the actuator piston 108 and cause movement of the piston from the orifice plate 14-6. Circular seal 14 8 is thus disengaged and the high actuating pressure is released substantially instantaneously upon the area of piston 168 outside circular seal 14%. A great net force is thus suddenly applied to the piston and impels it from the orifice plate with extremely high acceleration. The force and acceleration of the piston and the thrust column 11% are functions of the pressures in chambers 96 and 110, the piston and thrust column masses, and the ratio between the piston areas upon which the pressures act.

In operation the rapid downward acceleration of piston 108 causes an upward reaction on the remainder of the assembly. While the forces exerted within the housing by the actuating pressure become unbalanced upon downward movement of the piston from the orifice plate, the forces on the orifice plate 146 become balanced and an accelerating force is exerted upward on end plate 126. This force on end plate 126 is transmitted to the actuator housing and to the frame structure 12, that thereby feel an upward force simultaneously with the rapid downward acceleration of the thrust column 113. The mass of the frame structure 12 and the housing being large relative to the mass of the actuator piston 108 and thrust column 118, its high inertia restricts its movement against shock absorber 2 34. Thus the heavy frame and housing absorb the portion of reaction energy developed in accelerating column 118 and pass the remainder of the force or energy through shock absorber assembly 234- to the foundation 142. The upward movement of the reaction assembly is resisted by the shock absorber 234, which decelerates the frame structure 12 by forcing oil through the restricted orifices in orifice ring 2146, in a manner Well known in the art.

After impact and downward movement of the frame structure 12. and actuator column 118, the frame structure 12 and actuator column 118 is decelerated and the frame is then urged upward to its normal centered position by the pressures in the housing. The setting pressure in chamber 116 urges the actuator piston 168 upward against orifice plate 146. The pressures in the sealed pneumatic chambers 256 and 258 of the shock absorber assembly 234 also exert a centering force on the frame structure. A pressure differential between the two chambers 256 and 258 is produced by frame movement off center and exerts a centering force which assists in repositioning the frame relative to the foundation. The position of annular pistons 24-6 and 248, shown in FIGURE 3, correspond to the center positions or" the frame in actuator housing shown in FIGURE 1. To reset the actuator for repeated operation the actuator piston 168 is reseated against the orifice plate 146 to reestablish pressure sealin s by means of resilient seal 143. 'Reseating is normally effected by reducing the pressure in chamber 96 to a value below the pressure in chamber ldtl. The latter pressure then moves the piston 1'63 to the orifice plate 146.

The bounce shock eliminator means or assembly 28 is mounted on the impacting thrust means or column 118. (See FIGURES l and 2.) When the impacting column 118 is accelerated in the manner previously described, it will create a force that impacts through the assembly 28 against the bolster 132. causing work to be performed on the workpiece 138. The assembly 28 will be telescoped during this operation and will afford elimination of impact shock from bouncing of column 118 in the manner hereinafter described. FIGURES 4 through 6 illustrate the various conditions of the assembly 28 during the stages of the forming operation of the impacting machine. In FIGURE 4 the assembly .23 has an initial loaded condition. In FIGURE 5 the assembly 28 has reacted to the impaotin g stroke and FIGURE 6 illustrates the condition of the assembly 28 at that interval immediately following impact when the shock of rebound is being passed back to impacting column 118.

The assembly 28 is mounted on a ram Weight 34 by bolts 72 in the manner shown in FIGURES 4 through 6 and ram weight 34 is integral with the impacting column 118. A recess 56 on cylindrical member 36, hereafter referred to as cylinder, coacts with a pin on the ram weight 34 to align the cylinder 36 with the ram Weight. A piston 38 is carried in sliding relationship in the cylinder 36. Piston ring 4 8, that may be constructed of laminated bronze or other similar type materials, serves as a bearing between the piston 38 and the inner surface of cylinder 36. A sealing O-ring 50 effects pressure sealing between the piston 38 and cylinder 36. Piston 38 is prevented from sliding out of cylinder "38 by coaction of shoulder '43 with retaining ring 40'. The retaining ring 40 which is constructed in two parts for easy installation into the assembly is secured to the cylinder 36 by screws 68. A split bronze laminated bearing 52 is secured to the inner circumferential surface of ring 40 and permits an aligned sliding of the piston 38 within split retaining ring ill. The bearing 52 does not act as a seal, accordingly air may flow in and out of space 42 with little restriction. In operation, piston 38 is capable of moving from contact between the inner surface 51 of the closed end of cylinder 36 and contact between. shoulder 43 and retaining ring at Dowel pin 62 is secured to piston 38 and is capable of telescopic movement within cavity 37 of cylinder 36. The dowel pin 62 functions as an additional means for maintaining the correct alignment of the piston relative to the cylinder 36 during movement of the piston 38 within cylinder 36. Passageway 69 connects cavity 37 to the atmosphere permitting free flow of air therebetween. The passageway 76 in the piston 33 provides access to cap screw 68 and bolts 66 secure the die retaining means 71 to the outer end surface of piston 38. Aperture 58 co acts with a centering pin upon the die or die retaining means for alignment.

When piston 38 is in its outwardly extended telescopic position, as shown in FIGURE 4, a space 39 exists between the inner surface 51 of the closed end of cylinder 36 and the inner end surface 49 of piston 38. A passageway 41 passes through the cylinder 36, as shown, to allow air under pressure to be injected therein from an outside source of pressure (not shown). It is thus possible, by injecting pressurized air through passage 41 to space 39, to selectively cause piston 38 to move away from inner surface 51 to its extended position that is limited by shoulder 43 contacting retaining ring 40. As previously stated 0 ring 50 maintains a pressure sealed condition within space 39.

The inner end surface of piston 38 has a cylindrically shaped cavity or recess 46 having beveled edges 54 that smooth out the contact of surface recess 46 with surface -49. Recess 46 functions to receive the air existing Within space 39 when the piston 38 is telescoped against cylindrical surface 51 during the impact stroke. An inlet control valve 74 connected to passageway 41, see FIGURE 7, is of the type that will allow air under pressure to be injected into the space 39 but opposes the flow of air out of space 39 unless the pressure of the air exceeds a predetermined value. Thus during the telescoping movement of piston 38, as shown in FIGURE 5, the initially loaded air pressure placed in space 39 through passageway 41 is caused to compress into space 46 and thus aid in performing the bounce shock elimination as will be more completely understood hereinafter. It should be understood that recess 46 may be placed either in the piston surface 49 or in the cylindrical surface 51 and may have any desired configuration. However it is preferred that recess 46 have a relatively small diameter and thereby retain as much as possible the end surface 49 of piston 38 for contact with surface 51 during impact.

Attached to the outer end of piston 38 is a means 71 for securing the die hold ng member 144 to the piston 38. Die 145, held by die retaining member 144, coacts with die 136 that is held to bolster 132 by retaining member 134. Workpiece 133 is the billet to (be formed. The workpiece is compressed between dies 145 and 13d during the impact stroke and is formed to the desired configuration in a manner Well known in the art. Cylinder 36 and piston '38 are recessed inwardly at three points 59 to receive guide rods 30 (see FIGURE 7). The guide rods 34 aid in guiding the impacting column did during the impact stroke. The recesses also aid in the assembly of the cylinder 36 with the ram weight 34'. If necessary, bearings can be inserted into recesses 59 to reduce the friction of contact between cylinder 3% and guide rods 33. Retaining ring 40, shown in phantom in FIGURE 7, comprises pairs of opposing semicircular members having a space 47 therebetween. The space 47 aids in installation of the ring 49 and further assures free how of air therethrough to space 42.

In FIGURE 4 the assembly 28 is shown in its initial extended stage prior to the impacting of column 118 against the workpiece supported by the bolster 130. In this stage, air has been injected under pressure through passage 41 to the space 39 between the inner surface 51 of the closed end of cylinder 36 and end surface 49 of piston 38. If the piston 38 is not in the extended position the air pressure will cause piston 38 to be forced to its outwardly extended position to an extent that shoulder 43 rests against retaining ring 40.

When the impacting machine drives impacting column 118, mass 34 and assembly 28 against the bolster 130, the initial contact of die 145 against the billet 138 causes the piston 38 to telescope within the cylinder 35 with such force that the piston surface 49 moves into direct metal to metal contact with the inner cylindrical surface 51, see FIGURE 5. This movement of the piston 38 causes the air that occupied space 39 to be compressed within recess 46 as valve 74 opposes outward flow of air through passage 41. The metal to metal contact between the piston 38 and the cylinder 36 assures that the full force of the impacting column 118 is brought to hem in the forming operation on billet 138.

In the instant immediately following the initial impact, there remains in impacting column .118 a force or momentum that was not expended in forming the billet 138 to the desired-end configuration. This remaining momentum will tend to cause a rebound effect wherein the impacting column 118 will bounce away from the point of impact, which without the bounce eliminator assembly 28 would pull die 145 away from the billet 138. The remaining momentum of column 118 plus the pressure within the driving chamber llltl would then cause the impacting column 118 and die 14-5 to again impact billet 138 causing further deformation of billet 138 to occur. The bounce eliminator assembly 28 in eliminating the aforesaid rebound immediately in the instant of rebound expands telescopically under the torce of the air compressed within recess 46. This movement of piston 38 outwardly from cylinder 36 lengthens the impacting col umn to the extent that the die 145 is continuously held in contact with billet 138 and no separation therebetween occurs. Also the air that expands into space 3h creates an air cushioning medium between the cylinder 36 and piston 38 (see FIGURE 6). The air in space 39 has suificient retained pressure to create an air shock absorbing medium capable of preventing further contact of the surface 51 with the end surface 49 of piston 38. Thus no further metal to metal contact of the piston with the cylinder occurs and further impact shock on the Work through rebounding of the impact column in substantially eliminated. The cushioning of the rebounding effect passes the shock of rebound back into the impacting column 118. While a pressing force is impressed to a small degree upon the work, it is not suflicient to cause further deformation of the billet 138 to occur.

FIGURE 8 illustrates a modification wherein the impact bounce shock eliminator assembly 28 is positioned between the bolster 132 and die 138 rather than being positioned in the impacting column between ram Weight 34 and die 145. The operation of the assembly 233 is the same in this position as that described in FIGURES 4 and through 6. The piston 38 will be initially separated from the cylinder 36, will move into metal to metal contact with the cylinder 38 upon impact and will subsequently telescopically expand to hold the dies against the billet to provide a cushioned air pressure to absorb the rebounding shock.

What I claim is:

l. in combination, an impacting machine for forming materials through impact comprising, bolster means, impacting thrust means for impacting said materials against said bolster means in a forming impact stroke, shock eliminator means coacting with said impacting thrust means and said bolster means for substantially eliminating the application of rebound shock to said materials following said impact stroke, said shock eliminator means having a cylindrical member with an open end and a closed end, a piston member slidably mounted in said cylindrical member with a portion extending through said open end of said cylindrical member, said piston member being capable of movement within said cylindrical member between a position contacting the inner portion of said closed end of said cylindrical member and a position near the open end of said cylindrical member, said portion of said piston member extending through said open end of said cylindrical member having an outer extremity that is adjacent the cylindrical wall of said cylindrical member, at least one recess in said cylindrical wall, dowel pin means connected to said outer extremity of said piston member and slidably projecting into said recess in said cylindrical Wall for maintaining alignment between said piston member and said cylindrical member during relative movement therebetween, said piston member having a shoulder portion extending radially inwardly from the piston surface that contacts the inner surface of said cylindrical member, retainer ring means secured to said open end of said cylindrical member and substantially encircling said piston member for coacting with said shoulder portion to retain said piston member Within said cylindrical member, pressure means including a passageway through said cylindrical member for projecting a pressurized medium between said piston member and said inner surface of said closed end of said cylindrical member forcing said piston member to a position where said shoulder portion engages said retaining ring means, said pressure means having valve means for passing said pressurized medium to said passageway but opposing reverse movement of said medium when the pressure of said medium is below a given value, a part of said area between the end of said piston member and said closed end of said cylindrical member being recessed to provide an open space when the end of said piston member is in contact with said inner portion of said closed end of said cylindrical member, said open space having a volume capable of receiving said pressurized medium when said end of said piston is in contact with said inner portion of said closed end of said cylindrical member, the part of said area recessed to provide said open space being substantially smaller than the part of said area wherein the end of said piston contact said inner portion of said closed end of said cylindrical member and means for securing said shock eliminator means between said impacting thrust means and said bolster means in a manner that said piston is telescoped within said cylindrical member when said impacting thrust means is moved against said bolster in said impact stroke.

2. In combination, an impacting machine for forming materials through impact comprising, bolster means, impacting thrust means for impacting said materials against said bolster means in a forming impact stroke, shock eliminator means coacting with said impacting thrust means and said bolster means for substantially eliminating the application of rebound shock to said materials following said impact stroke, said shock eliminator means having a cylindrical member with an open end and a closed end, a piston member slidably mounted in said cylindrical member with a portion extending through said open end of said cylindrical member, said piston member being capable of movement within said cylindrical member between a position contacting the inner portion of said closed end of said cylindrical member and a position near the open end of said cylindrical member, alignment means 'for maintaining alignment between said piston member and said cylindrical member during sliding movement therebetween, said piston member having a shoulder portion extending radially inwardly from the piston surface that contacts the inner surface of said cylindrical member, retainer ring means secured to said open end of said cylindrical member and substantially encircling said piston member for coacting with said shoulder portion to retain said piston member within said cylindrical member, means for conducting a pressurized medium between said end of said piston and said inner portion of said closed end of said cylindrical member, a part of said area between the end of said piston member and said closed end of said cylindrical member being recessed to provide an open space when the end of said piston member is in contact with said inner portion of said closed end of said cylindrical member, said open space having a volume capable of receiving said pressurized medium when said end of said piston is in 'contact with said inner portion of said closed end of said cylindrical member, the part of said area recessed to provide said open space being substantially smaller than the part of said area wherein the end of said piston contacts said inner portion of said closed end of said cylindrical member and means for securing said shock eliminator means between said impacting thrust means and said bolster means in a manner that said piston is telescoped within said cylindrical member when said impacting thrust means is moved against said bolster in said impact stroke.

3. In combination an impacting machine for forming materials through impact comprising, bolster means, impacting thrust means for impacting said materials against said bolster means in a forming impact stroke, shock eliminator means coacting with said impacting thrust means and said bolster means for substantially eliminating the application of rebound shock to said materials following said impact stroke, said shock eliminator means having a cylindrical member with an open end and a closed end, a piston member slidably mounted in said cylindrical member with a portion extending through said open end of said cylindrical member, said piston member being capable of movement within said cylindrical member between a position contacting the inner portion of said closed end of said cylindrical member and a position near the open end of said cylindrical member, said piston member having a shoulder portion extending radially inwardly from the piston surface that contacts the inner surface of said cylindrical member, retainer ring means secured to said open end of said cylindrical mem ber and substantially encircling said piston member for coacting with said shoulder portion to retain said piston member within said cylindrical member, means for conducting a pressurized medium between said end of said piston and said inner portion of said closed end of said cylindrical member, a part of said area between the end of said piston member and said closed end of said cylindrical member being recessed to provide an open space when the end of said piston member is in contact with said inner portion of said closed end of said cylindrical member, said open space having a volume capable of receiving said pressurized medium when said end of said piston is in contact with said inner portion of said closed end of said cylindrical member, and means for securing 1% said shock eliminator means between said impacting thrust means and said bolster means in a manner that said piston is telescoped within said cylindrical member when said impacting thrust means is moved against said bolster in said impact stroke.

4. In combination an impacting machine for forming materials through impact comprising, bolster means, impacting thrust means for impacting said materials against said bolster means in a forming impact stroke, shock eliminator means coacting with said impacting thrust means and said bolster means for substantially eliminating the application of rebound shock to said materials following said impact stroke, said shock eliminator means having a cylindrical member with an open end and a closed end with said closed end secured to said impacting thrust means, a piston member slidably mounted in said cylindrical member with a portion extending through said open end of said cylindrical member, said piston member being capable of movement within said cylindrical member between a position contacting the inner portion of said closed end of said cylindrical member and a position near the open end of said cylindrical member, said portion of said piston member extending through said open end of said cylindrical member having an outer extremity that is adjacent the cylindrical wall of said cylindrical member, at least one recess in said cylindrical wall, dowel pin means connected to said outer extremity of said piston member and slidably projecting into said recess in said cylindrical wall for maintaining alignment between said piston member and said cylindrical member during relative movement therebetween, said piston member having a shoulder portion extending radially inwardly from the piston surface that contacts the inner surface of said cylindrical member, retainer ring means secured to said open end of said cylindrical member and substantially encircling said piston member for coacting with said shoulder portion to retain said piston member within said cylindrical member, pressure means including a passageway through said cylindrical member for projecting a pressurized medium between said piston member and said inner surface of said closed end of said cylindrical member forcing said piston member to a position where said shoulder portion engages said retaining ring means, said pressure means having valve means for passing said pressurized medium to said passageway but opposing reverse movement of said medium when the pressure of said medium is below a given value, a part of said area between the end of said piston member and said closed end of said cylindrical member being recessed to provide an open space when the end of said piston member is in contact with said inner portion of said closed end of said cylindrical member, said open space having a volume capable of receiving said pressurized medium when said end of said piston is in contact with said inner portion of said closed end of said cylindrical member, the part of said area recessed to provide said open space being substantially smaller than the part of said area wherein the end of said piston contacts said in ner portion of said closed end of said cylindrical member and means for securing said shock eliminator means between said impacting thrust means and said bolster means in a manner that said piston is telescoped within said cylindrical member when said impacting thrust means is moved against said bolster in said impact stroke.

5. A shock eliminator for substantially eliminating rebound shock in impacting machines comprising, a cylindrical member with an open end and a closed end, a piston member slidably mounted in said cylindrical member with a portion extending through said open end of said cylindrical member, said piston member being capable of movement within said cylindrical member between a position contacting the inner portion of said closed end of said cylindrical member and a position near the open end of said cylindrical member said portion of said piston member extending through said open end of said c ll lindrical member having an outer extremity that is adjacent the cylindrical wall of said cylindrical member, at least one recess in said cylindrical wall, dowel pin means connected to said outer extremity of said piston member and slidably projecting into said recess in said cylindrical wall for maintaining alignment between said piston member and said cylindrical member during relative movement therebetween, said piston member having a shoulder portion extending radially inwardly from the piston surface that contacts the inner surface of said cylindrical member, retainer ring means secured to said open end of said cylindrical member and substantially encircling said piston member for coacting with said shoulder portion to retain said piston member within said cylindrical member, pressure means including a passageway through said cylindrical member for projecting a pressurized medium between said piston member and said inner surface of said closed end of said cylindrical member forcing said piston member to a position where said shoulder portion engages said retaining ring means, said pressure means having valve means for passing said pressurized medium to said passageway but opposing reverse movement of said medium when the pressure of said medium is below a given value, a part of said area between the end of said piston member and said closed end of said cylindrical member being recessed to provide an open space when the end of said piston member is in contact with said inner portion of said closed end of said cylindrical member, said open space having a volume capable of receiving said pressurized medium when said end of said piston is in contact with said inner portion of said closed end of said cylindrical member, and the part of said area recessed to provide said open space being substantially smaller than the part of said area wherein the end of said piston contacts said inner portion of said closed end of said cylindrical member.

References Cited in the file of this patent UNITED STATES PATENTS 486,772 Evans Nov. 22, 1892 2,007,290 Treer July 9, 1935 2,842,357 Williamson July 8, 1958 2,918,272 Williamson Dec. 22, 1959 3,036,538 Ottestad May 29, 1962 FOREIGN PATENTS 414,012 France Mar. 24, 1910 462,116 Great Britain Mar. 1, 1937 

1. IN COMBINATION, AN IMPACTING MACHINE FOR FORMING MATERIALS THROUGH IMPACT COMPRISING, BOLSTER MEANS, IMPACTING THRUST MEANS FOR IMPACTING SAID MATERIALS AGAINST SAID BOLSTER MEANS IN A FORMING IMPACT STROKE, SHOCK ELIMINATOR MEANS COACTING WITH SAID IMPACTING THRUST MEANS AND SAID BOLSTER MEANS FOR SUBSTANTIALLY ELIMINATING THE APPLICATION OF REBOUND SHOCK TO SAID MATERIALS FOLLOWING SAID IMPACT STROKE, SAID SHOCK ELIMINATOR MEANS HAVING A CYLINDRICAL MEMBER WITH AN OPEN END AND A CLOSED END, A PISTON MEMBER SLIDABLY MOUNTED IN SAID CYLINDRICAL MEMBER WITH A PORTION EXTENDING THROUGH SAID OPEN END OF SAID CYLINDRICAL MEMBER, SAID PISTON MEMBER BEING CAPABLE OF MOVEMENT WITHIN SAID CYLINDRICAL MEMBER BETWEEN A POSITION CONTACTING THE INNER PORTION OF SAID CLOSED END OF SAID CYLINDRICAL MEMBER AND A POSITION NEAR THE OPEN END OF SAID CYLINDRICAL MEMBER, SAID PORTION OF SAID PISTON MEMBER EXTENDING THROUGH SAID OPEN END OF SAID CYLINDRICAL MEMBER HAVING AN OUTER EXTREMITY THAT IS ADJACENT THE CYLINDRICAL WALL OF SAID CYLINDRICAL MEMBER, AT LEAST ONE RECESS IN SAID CYLINDRICAL WALL, DOWEL PIN MEANS CONNECTED TO SAID OUTER EXTREMITY OF SAID PISTON MEMBER AND SLIDABLY PROJECTING INTO SAID RECESS IN SAID CYLINDRICAL WALL FOR MAINTAINING ALIGNMENT BETWEEN SAID PISTON MEMBER AND SAID CYLINDRICAL MEMBER DURING RELATIVE MOVEMENT THEREBETWEEN, SAID PISTON MEMBER HAVING A SHOULDER PORTION EXTENDING RADIALLY INWARDLY FROM THE PISTON SURFACE THAT CONTACTS THE INNER SURFACE OF SAID CYLINDRICAL MEMBER, RETAINER RING MEANS SECURED TO SAID OPEN END OF SAID CYLINDRICAL MEMBER AND SUBSTANTIALLY ENCIRCLING SAID PISTON MEMBER FOR COACTING WITH SAID SHOULDER PORTION TO RETAIN SAID PISTON MEMBER WITHIN SAID CYLINDRICAL MEMBER, PRESSURE MEANS INCLUDING A PASSAGEWAY THROUGH SAID CYLINDRICAL MEMBER FOR PROJECTING A PRESSURIZED MEDIUM BETWEEN SAID PISTON MEMBER AND SAID INNER SURFACE OF SAID CLOSED END OF SAID CYLINDRICAL MEMBER FORCING SAID PISTON MEMBER TO A POSITION WHERE SAID SHOULDER PORTION ENGAGES SAID RETAINING RING MEANS, SAID PRESSURE MEANS HAVING VALVE MEANS FOR PASSING SAID PRESSURIZED MEDIUM TO SAID PASSAGEWAY BUT OPPOSING REVERSE MOVEMENT OF SAID MEDIUM WHEN THE PRESSURE OF SAID MEDIUM IS BELOW A GIVEN VALUE, A PART OF SAID AREA BETWEEN THE END OF SAID PISTON MEMBER AND SAID CLOSED END OF SAID CYLINDRICAL MEMBER BEING RECESSED TO PROVIDE AN OPEN SPACE WHEN THE END OF SAID PISTON MEMBER IS IN CONTACT WITH SAID INNER PORTION OF SAID CLOSED END OF SAID CYLINDRICAL MEMBER, SAID OPEN SPACE HAVING A VOLUME CAPABLE OF RECEIVING SAID PRESSURIZED MEDIUM WHEN SAID END OF SAID PISTON IS IN CONTACT WITH SAID INNER PORTION OF SAID CLOSED END OF SAID CYLINDRICAL MEMBER, THE PART OF SAID AREA RECESSED TO PROVIDE SAID OPEN SPACE BEING SUBSTANTIALLY SMALLER THAN THE PART OF SAID AREA WHEREIN THE END OF SAID PISTON CONTACT SAID INNER PORTION OF SAID CLOSED END OF SAID CYLINDRICAL MEMBER AND MEANS FOR SECURING SAID SHOCK ELIMINATOR MEANS BETWEEN SAID IMPACTING THRUST MEANS AND SAID BOLSTER MEANS IN A MANNER THAT SAID PISTON IS TELESCOPED WITHIN SAID CYLINDRICAL MEMBER WHEN SAID IMPACTING THRUST MEANS IS MOVED AGAINST SAID BOLSTER IN SAID IMPACT STROKE. 